This invention is in the field of burners and particularly gaseous fuel burners for furnaces.
Heretofore furnace burners were often operated under ambient atmospheric conditions where gas and primary air were mixed in a venturi and an excess of secondary air was supplied to the combustion chamber. The drawback to using this approach is that all excess air, which must be supplied to ensure proper combustion, increases flue losses and thus reduces the unit efficiency.
There has also been used power burners having a single port, where gas and air are mixed in a chamber. The gas and air mixture is then burned in a concentrated flame at a single location. The drawback to using this approach is that the flame is concentrated in one location instead of being spread over a large area of heating surface.
It has also been proposed to supply secondary air to a gaseous fuel burner by directing secondary air along a path different from the path followed by the fuel and air mixture. See, for example, the U.S. patent to Ross No. 3,156,292 and also see the U.S. patent to Craig et al No. 3,837,788 wherein the primary air for combustion and the secondary air is supplied from a common chamber. The U.S. patents to Flynn and Flynn et al Nos. 2,428,274, 3,499,720, and 2,647,569 propose to construct burners from sheet metal components.